Clinton entered the hearing room at 10 a.m. and greeted the panel's chairman, Rep. Trey Gowdy of South Carolina, and other members.

Clinton's the Democratic front-runner for president. She's testifying on the deadly 2012 attacks in Benghazi, Libya, that killed four Americans. Clinton was secretary of state at the time.

Her testimony is a key moment for Clinton as she seeks to solidify her hold on the Democratic nomination. It is also crucial for the committee, which has seen its credibility eroded in recent weeks. Republican lawmakers including House Majority Leader Kevin McCarthy have credited the panel with bringing down Clinton's poll numbers.